Rotary concrete saws used in construction and repair of highways, airport runways, and large concrete foundations are well known. Usually these are self-propelled units in which an operator walks behind the unit, the longitudinal propulsion of the unit and the rotation of the saw blade being achieved by pulleys connected through suitable gearing systems to a prime mover. The propulsion speed of the device and the rotational speed of the saw blade may be manually controlled by the operator. Concrete will vary in density, depending upon the ingredients used in making the concrete mix and in large area installations, such as highways, airport runways, warehouse floors, etc., the density of the concrete can vary considerably.
In addition, in operating a concrete saw, oftentimes the saw blade will encounter reinforcing bars which must also be cut through and, of course, are far denser than concrete.
In cutting through concrete, it is desirable to have the surface speed of the blade at an optimum amount. This speed will vary from 9000 to 12000 feet per minute depending upon the diameter of the blade and the aggregate being cut.
Concrete blades used for this purpose have diamond cutting edges and are very expensive, costing about $1,200. If the blade is operated at other than an optimum speed, the cutting edge will wear down at a much more rapid rate thus dramatically increasing the cost of operation.
In the devices of the prior art the surface speed of the blade and the transverse speed of the saw platform are manually controlled by the operator so that when varying densities of the material being cut are encountered, the judgment of the operator is relied upon to slow the transverse movement of the saw platform or to modify the speed of the blade, or both, and, of course, the manner in which this is done will vary from operator to operator, depending upon their experience.